1. Field of the Invention
This invention relates to a remote access program, a remote access request-processing program, and a client computer, for carrying out remote access, and more particularly to a remote access program, a remote access request-processing program, and a client computer, for using a storage device connected to a plurality of server computers.
2. Description of the Related Art
As a file system enabling resources to be used in a shared manner via a network, NFS (Network File System) is generally used. In an NFS network, a storage device is connected to a server computer (hereinafter, simply referred to as “the server”). This storage device is provided for use by another client computer (hereinafter simply referred to as “the client”) connected to the storage device via the network as a resource on the server.
A client which makes use of the NFS mounts a resource on the server at a mount point on the client (in the case of a UNIX (registered trademark)-based OS (Operating System)). This enables the user of the client to access the resource on the server via the mount point, in the same manner as in the local file system. At this time, only one server can be designated for one mount point.
By the way, as a system which enables the direct shared use of a storage device, such as a magnetic disk, from a plurality of nodes of a network, a SAN (Storage Area Network) has been conventionally used. The SAN is capable of causing the whole network to serve as a file server. In this case, a plurality of servers constituting the SAN can each play the roll of a file server. At this time, a client can access the storage device provided by the SAN by designating a desired one of the servers for one mount point.
It should be noted that there is a case in which a large number of clients are connected to a network. In such a case, for each client to access a resource on servers constructed by the SAN, by the NFS, it is necessary to distribute designated servers among the servers on a client-by-client basis or a mount point-by-mount point basis, so as to prevent load from being concentrated on one server.
However, even if the designated servers providing access to the resource are distributed among the servers on a client-by-client basis or a mount point-by-mount point basis, the biased or non-uniform use by the clients can result in a large number of accesses which are made via only one specific server. That is, if a plurality of clients which have designated the same server simultaneously accesses the resource provided by the SAN, even if the other servers are each well within the processing capacity thereof, the access is only permitted via the server designated by the clients beforehand. Therefore, even when the SAN as a whole is well within the processing capacity, the processing speed is lowered.
Further, assuming that the servers are distributed on a client-by-client basis, if the same resource is accessed by them, the same file (data) are controlled by the plurality of servers, which makes it difficult to ensure the consistency of the file (data).
Further, there is a strong demand for a system in which a processing request from a client which has designated a server as an access point is automatically switched to another server, in the event that the server has undergone a system shut down due to failure or the like.